An early cyclone method and apparatus is known from U.S. Pat. No. 453,105 (Bretney) issued May 26, 1891. Various hydrocyclone separators have been described later in many patents. All those positive pressure hydrocyclones have low separation efficiency, high pressure drop and high water contents in underflow solid product. To increase the hydrocyclone separation efficiency, an artificial air core was invented (Wlodzinierz J. Tuszko et al, Patent No. 4,927,298 issued May 22, 1990). To increase the air cyclone (cyclone dust collector) separation efficiency an air core cyclone was invented (Wlodzinierz J. Tuszko et al, application of 07/360117 Ser. No. 07/651033 filed Jan. 30, 1991). Up to now, all hydrocyclone types were fed pressurewise that means the pump is pressing the feed suspension into the cyclone inlet. The air cyclone or cyclone dust collector can be fed pressurewise (positive pressure cyclone) as well as suctionwise (negative pressure cyclone). By then, negative pressure cyclone, the pump is sucking the feed suspension into the cyclone inlet. The inlet of the positive pressure cyclone is connected to the pressure pipe of the feeding pump air blower. The outlet of the negative pressure cyclone is connected to the suction pipe of the feeding blower. The negative pressure hydrocyclone was not used up to now apparently because there was no solution to take away the heavier or coarser product from the hydrocyclone's negative pressure interior and because of a low separation efficiency. The pressure drop of the present used positive pressure hydrocyclone generally ranges from 5 to 50 psig depending upon the particular hydrocyclone size and its capacity. The fluid content in the underflow solid product of this kind hydrocyclone is about 60% to 75%.
It would, therefore, be desirable to provide the negative pressure hydrocyclone to reduce the pressure loss called the pressure drop, between the cyclone inlet duct and exhaust pipe to reduce the energy consumption.
It would further be advantageous to exploit the negative pressure in hydrocyclone for a deep dewatering of the underflow solid product.
It would also be desirable to increase the operational life of the hydrocyclone feeding pump and to allow a feed pump to feed simultaneously both negative and positive pressure hydrocyclones.
It would further be desirable to allow for the use of the negative pressure hydrocyclone as a water cleaner for submerged pumps such as for cleaning water for agricultural purposes like irrigation.